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ID Date Author Typeup Category Subject
  13494   Sun Dec 31 12:43:50 2017 ranaSummaryElectronicsSR560: reworking

I have ordered some LSK389A (in both the SOIC-8 and TO-71 packages) to replace the SR560's default front end FET pair (NPD5565).

I'm going to rework s# 00619 once these new FETs come in. Also ordered 100 of the SOIC-8 to DIP-8 adapter boards from Digikey.

This plot shows the current performance compared to the Rai Low Noise box. I expect the FETs should let us get to ~1.5 nV/rHz with the SR560.

Attachment 1: Preamps.pdf
Preamps.pdf
  13516   Mon Jan 8 20:50:01 2018 ranaSummaryElectronicsSR560: reworking

I replaced the NPD5565 with a LSK389 (SOIC-8 with DIP adapter). There was a noise reduction of ~30%, but not nearly as much as I expected. I wonder if I have to change the DC bias current on these to get the low noise operation?

https://photos.app.goo.gl/hsMwsif7NLscsgpx1

  13544   Fri Jan 12 20:35:34 2018 Udit KhandelwalSummaryGeneral2018/01/12 Summary
  1. 40m Lab CAD
    1. Worked further on positioning vacuum tubes and chambers in the building.
    2. Next step would be to find some drawings for optical table positions and vibration isolation stack. Need help with this! 
  2. Tip Tilt Suspension (D070172)
    1. Increased the length of side arms. The overall height of D070172 assembly matches that of D960001.
    2. The files are present in dropbox in [40mShare] > [40m_cad_models] > [TT - Tip Tilt Suspension]
  13560   Fri Jan 19 15:22:19 2018 Udit KhandelwalSummaryGeneral40m CAD update 2018/01/19

40m CAD Project

  1. All parts will be now named according to the numbering system in this excel sheet: LIGO 40m Parts List in dropbox folder [40mShare] > [40m_cad_models] > [40m Lab CAD]
  2. I've placed optical tables in the chambers at 34.82" from the bottom for now. This was chosen by aligning the centre of test mass of SOS assembly (D960001) with that of vacuum tube (Steve however pointed out last week they might not necessarily be concentric).

  13566   Mon Jan 22 12:48:48 2018 KojiSummaryGeneralBeat setup for aLIGO EOM test

I'm planning to construct a beat setup between the PSL and AUX beams. I am going to make it in the area shown in a blue square in the attached photo. This does not disturb Johannes' and PSL setups. The beams are obtained from the PBS reflection of the PSL and the dumped beam of the aux path (0th or 1st order beam of the AOM).

Attachment 1: IMG_3048.JPG
IMG_3048.JPG
  13567   Mon Jan 22 20:54:58 2018 KojiSummaryGeneralAUX-PSL beat setup

The beat setup has been made on the PSL table. The BS and the PD were setup. The beat was found at 29.42degC and 50.58degC for the PSL and AUX crystal temperatures, respectively.
We are ready for the EOM test. I have instruments stacked around the PSL table. Please leave them as they are for a while. If you need to move them, please contact with me. Thanks.


A picked-off PSL after the main modulator was used as the PSL beam. This was already introduced close to the setup thanks to the previous 3f cancellation test ELOG 11029. The AUX beam was obtained from the transmission of 90% mirror. Both paths have S polarization. The beams are combined with a S-pol 50% BS. The combined beam is detected by a new focus 1GHz PD.

The PSL crystal temp (actual) was 50.58degC. The AUX crystal temp was swept upward and the string beat was found at 50.58degC. After a bit of alignment, the beat strength was -18dBm (at 700V/A RF transimpedance of NF1611) .

Attachment 1: IMG_3051.JPG
IMG_3051.JPG
  13575   Wed Jan 24 13:55:04 2018 KiraSummaryPEMSeismometer can insulation test

Gautam and I set up the insulated seismometer can in the lab today. I had previously wired up the two heaters I placed onto the sides of the can in parallel to get a total resistance of 12.5 ohms and then I wrapped the whole can in 3 layers of insulation (k-factor 0.25). We placed it on a large sheet of insulation as to not crush the wires leading out the bottom of the can. I stuck on one of my AD590 sensors to the inside of the can onto the copper lining using duct tape, though this is only a temporary solution. In the future, it would be nice to have some sort of thermal clamp to secure the sensor to the can. To provide power to the heater circuit board and the temperature sensor board, we got a powerstrip and plugged in two power supplies and a function generator into it. The heater circuit (attachment 3) is powered by one of the power supplies and the function generator, while the temperature sensor (attachment 5) is stuck to the side of the can and is powered by the second power supply. The heater circuit's MOSFET (IRF640, attachment 4) is placed on a metal block and sandwiched between two more to make sure it doesn't move around. The temperature sensor is connected by a long BNC cable to the channels in attachment 6.


gautam: we plugged the BNC output of Kira's temperature sensor circuit to J7 on the AA input chassis in 1X2 - this corresponds to ADC1 input 12 in c1ioo. I then made a "PEM" namespace block inside the c1als model, and placed a single CDS filter module inside it (this can be used for calibration purposes). The filter module is named "C1:PEM-SEIS_EX_TEMP", and has the usual CDSfilt channels available. I DQ'ed the output of the filter module (@256 Hz, probably too high, but I'm holding off on a recompile for now). Recompilation and model restart of c1als went smoothly. 

2 bench power supplies are being used for this test, we can think of a more permanent solution later.

**25 Jan noon: Added another filter module, "C1:PEM-SEIS_EX_TEMP", to which Kira is hooking up a second temperature sensor, which will serve as a monitor of the "Ambient" lab temperature. Added DQ channel for the output of this filter module, fixed sampling to 32Hz. Compile and restart went smooth.

Attachment 1: IMG_20180124_124209.jpg
IMG_20180124_124209.jpg
Attachment 2: IMG_20180124_124202.jpg
IMG_20180124_124202.jpg
Attachment 3: IMG_20180124_124224.jpg
IMG_20180124_124224.jpg
Attachment 4: IMG_20180124_124229.jpg
IMG_20180124_124229.jpg
Attachment 5: IMG_20180124_124236.jpg
IMG_20180124_124236.jpg
Attachment 6: IMG_20180124_124156.jpg
IMG_20180124_124156.jpg
  13601   Fri Feb 2 21:12:46 2018 Udit KhandelwalSummaryGeneralSummary - 2018/02/02

Tip-Tilt Suspension CAD:
Discussed with Koji about motivation to simplify the design of this assembly, which has many unnecessary over-constraints. I have started to cad alternate parts with the aim of removing these over-constraints.

40m Lab CAD:
Acquired a stack of original engineering drawings of the vacuum chambers from Steve which I will take home, get scanned, and then use as reference for the cad i'm working on.

Other:
Started paperwork at west bridge office to get paid as an "occasional employee". Hopefully I receive old money.

  13602   Fri Feb 2 22:47:00 2018 KojiSummaryGeneralAP1053: Packaging & Performance

I've packaged an AP1053 in a Thorlabs box. The gain and the input noise level were measured. It has the gain of ~10 and the input noise of ~0.6nV/rtHz@50MHz~200MHz.

Details

AP1053 was soldered on Thorlabs' PCB EEAPB1 (forgot to take a picture). The corresponding chassis is Thorlabs' EEA17. There is a 0.1uF high-K ceramic cap between DC and GND pins. The power is supplied via a DC feedthru capacitor (Newark / Power Line Filter / 90F2268 / 5500pF) found in the WB EE shop. The power cable has a connector to make the long side of the wires detachable. Because I did not want to leave the RF signal path just mechanically touched, the SMA connectors were soldered to the PCB. As the housing has no access hole, I had to make it at one of the sides.

The gain of the unit was measured using the setup shown in the upper figure of Attachment 2. When the unit was energized, it drew the current of about 0.1A. The measued gain was compensated by the pick off ratio of the coupler (20dB). The gain was measured with the input power of -20, -10, 0, 10, and 15dBm. The measurement  result is shown in Attachment 3. The small signal gain was actually 10dB and showed slight degradation above 100MHz. At the input of 10dB some compression of the gain is already visible. It looks consistent with the specification of +26.0dBm output for 1dB compression above 50MHz and +24.0dBm output below 50MHz.

The noise level was characterized with the setup shown in the bottom figure of Attachment 3. The noise figure of the amplifier is supposed to be 1.5dB above 200MHz and 3.5dB below 200MHz. This is quite low and the output noise of AP1053 can not be measured directly by the analyzer. So, another LN amplifier (ZFL-500HLN) was stacked. The total gain of the system was measured in the same way as above. The measured noise level was ~0.7nV/rtHz between 50MHz and 200MHz. Considering the measurement noise level of the system, it is consistent with the input referred noise of 0.6nV/rtHz. I could not confirm the advertized noise figure of 1.5dB above 200MHz. The noise goes up below 50MHz. But still 2nV/rtHz at 3MHz. I'd say this is a very good performance.

Attachment 1: AP1053.JPG
AP1053.JPG
Attachment 2: AP1053_measurement.pdf
AP1053_measurement.pdf
Attachment 3: AP1053_gain.pdf
AP1053_gain.pdf
Attachment 4: AP1053_noise.pdf
AP1053_noise.pdf
  13638   Fri Feb 16 21:03:17 2018 Udit KhandelwalSummaryGeneralSummary 2018/02/16

40m Lab Cad:
Updated the dimensions of and fleshed out the chambers in greater detail, by referring to the engineering drawings that Steve gave to me. I have scanned and uploaded most of these drawings to Dropbox in [40mShare]>[40m_cad_models]>[Vacuum Chamber Drawing Scans]. The excel file "LIGO 40m Parts List" in the [40m Lab CAD] folder also lists the Steve drawings I referenced for dimensions of each part.


Next steps:
1. Finish details of all chambers.
2. Start placing representative blocks on the optical table.

  13654   Fri Feb 23 20:46:04 2018 Udit KhandelwalSummaryGeneralCAD Summary 2018/02/23

I have more or less finished cadding the test mass chamber by referring to the drawings Steve gave me. Finer details like lugs and bolts and window flaps can be left for later. Here's a quick render:

  13662   Wed Feb 28 21:14:34 2018 gautamSummaryPEMChannel admin

Since we decided to use the Acromag for readback of the temperature sensor for Kira's seismometer temperature control, I enabled logging of the channel Johannes had reserved for this purpose last week. Kira has made the physical connection of a temperature sensor to the BNC input for this channel - it reads back -2.92 V right now, which is around what I remember it being when Kira was doing her benchtop tests. I edited C0EDCU.ini to enable logging of this channel at 16 Hz. Presumably, a study of the ADC noise of the Acromag at low frequencies has to be made to ensure appropriate whitening (if any) can be added. Channel name is C1:PEM-SEIS_EX_TEMP_MON. Similarly, there is C1:PEM_SEIS_EX_TEMP_CTRL which is meant to be the control channel for the servoing. Calibration of the temperature sensor readback into temperature units remains. It also remains to be verified if we can have these slow EPICS channels integrated with a fast control model, or if the PID temperature control will be purely custom-script based as we have for the FSS slow loop.

I removed the fast channels I had setup temporarily in c1als. Recompilation and restart of the model went smoothly.

Quote:
 I then made a "PEM" namespace block inside the c1als model, and placed a single CDS filter module inside it (this can be used for calibration purposes). The filter module is named "C1:PEM-SEIS_EX_TEMP", and has the usual CDSfilt channels available. I DQ'ed the output of the filter module (@256 Hz, probably too high, but I'm holding off on a recompile for now). Recompilation and model restart of c1als went smoothly. 
 
Attachment 1: tempSensData.png
tempSensData.png
  13677   Fri Mar 9 20:35:41 2018 Udit KhandelwalSummaryGeneralSummary 2018/03/09

1. Optical Table Layout 

I had discussed with Koji a way to record coordinates of optical table equipments in a text file, and load to solidworks. The goal is to make it easier to move things around on the table in the CAD. While I have succeeded in importing coordinates through txt files, there is still a lot of tediousness in converting these points into sketches. Furthermore, the task has to be redone everytime a coordinate is added to or changed in the txt file. Koji and I think that this can all be automated through solidworks macros, so I will explore that option for the next two weeks.

2. Vacuum Chamber CADs 

Steve will help find manufacturing drawings of the BS chamber. I have completed the ETM chambers, while the ITM ones are identical to them so I will reuse parts for the CAD. 

  13683   Thu Mar 15 16:00:25 2018 Larry WallaceSummaryComputersCert renewal for NODUS

The cert for nodus has been renewed for another 2 years.

The following is the basic procedure for getting a new cert: (Note certs are only good for two years as of 2018)
openssl req -sha256 -nodes -newkey rsa:2048 -keyout nodus.ligo.caltech.edu.key -out nodus.ligo.caltech.edu.csr
Country Name (2 letter code) [AU]:US
State or Province Name (full name) [Some-State]:CaliforniaLocality Name (eg, city) []:Pasadena
Organization Name (eg, company) [Internet Widgits Pty Ltd]:California Institute of Technology
Organizational Unit Name (eg, section) []:LIGO
Common Name (eg, YOUR name) []:nodus.ligo.caltech.edu

Leave the e-mail address, challenge password and optional company name blank. A new private key will be generated.
chown root nodus.ligo.caltech.edu.key
chgrp root nodus.ligo.caltech.edu.key
chmod 0600 nodus.ligo.caltech.edu.key

The nodus.ligo.caltech.edu.csr file is what is sent in for the cert.
This file should be sent to either ryan@ligo.caltech.edu or security@caltech.edu and copy wallace_l@ligo.caltech.edu.

A URL llink with the new cert to be downloaded will be sent to the requestor.

Once the files are downloaded, the new cert and intermediate cert, they can be copied and renamed.

The PEM-encoded host certificate by itself is saved at:

  /etc/httpd/ssl/nodus.ligo.caltech.edu.crt

The nodus.ligo.caltech.edu.key file should be in the same directory or whichever directory is indicated in the ssl.conf located in /etc/httpd/conf.d/  directory.

httpd will need to be restarted in order for it to see the new cert.

 

  13686   Mon Mar 19 07:37:00 2018 Angelina PanSummary Proposed QPD Optical Arrangement

I am currently working on an optical arrangement consisting of a QPD that measures the fluctuations of an incoming HeNe laser beam that is reflected by a mirror. The goal is to add a second QPD to the optical arrangement to form a linear combination that effectively cancels out the (angular) fluctuations from the laser beam itself so that we can only focus on the fluctuations produced by the mirror.

In order to solve this problem, I have written a program for calculating the different contributions of the fluctuations of the HeNe laser and fluctuations from the mirror, for each QPD (program script attached). The goal of the program is to find the optimal combination of L0, L1, L2, and f2 that cancels the fluctuations from the laser beam (while retaining  solely the fluctuations from the mirror) when adding the fluctuations of QPD 1 and QPD 2 together. 

By running this program for different combinations of distances and focal lengths, I have found that the following values should work to cancel out the effects of the oscillations from the HeNe laser beam (assuming a focal length of 0.2 m for the lens in front of the original QPD):

  • L0 = 1.0000 m (distance from laser tube to mirror)
  • L1 = 0.8510 m (distance from mirror to lens in front of QPD 1)
  • L2 = 0.9319 m (distance from beamsplitter to lens in front of QPD 2)
  • f2 = 0.3011 m (focal length of lens in front of QPD 2)

Based on these calculations, I propose to try the following lens for QPD 2:

1’’ UV Fused Silica Plano-Convex Lens, AR-Coated: 350 - 700 nm (focal length 0.3011 m). https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=6508

Attachment 1: angelinaCode.py.tar.bz2
  13699   Thu Mar 22 17:47:16 2018 Angelina PanSummary Proposed QPD Optical Arrangement
Attachment 1: IMG_0869.jpg
IMG_0869.jpg
  13705   Mon Mar 26 21:25:55 2018 ranaSummaryIOOMC2 Trans table has issues

Gautam, Rana

While at the MC2 table, we noticed that it has some optical problems:

  1. There is an ND filter mounted to the beam reducing lens. ND filters are illegal, Steve. It causes too much scattering noise. We should instead have a beamsplitter and a dump.
  2. One of those bad U100-AC28 mounts is in use. This is one of those ones with plastic clips that Osamu liked, but the plastic gets in the way of the beam. Needs to be removed.
  3. Reflections from the QPD and the PDA255 are not dumped. This causes noise. Bad.
  4. The QPD transimpedance should be reduced so that it can handle more light. I don't know what it has now, but its probably 10-100 kOhm.

We estimated that the power in the IMC is (1 W)*Finesse/pi = 500 W. The MC2 Transmission spec is < 10 ppm, so the power on the table is probably ~5 mW. Since the PDA255 has a transimpedance of 10 kOhm and a max output power of 10V, it can handle up to ~1 mW. Probably we can get the QPD to handle 4 mW.

Gautam, Steve  3-27

We measured MC2 transmitted power right at the uncoated window ~2.5 mW  The beam was just a little bigger than the meter.

Attachment 1: 20180326_201929.jpg
20180326_201929.jpg
  13706   Mon Mar 26 21:40:26 2018 gautamSummaryIOOMC2 classical radiation pressure noise

[rana, gautam]

we measured the RIN of the MC2 transmission using the PDA255 I had put on the MC2 trans table sometime ago for ringdowns. Attached are (i) spectra for the RIN, (ii) spectra for the classical rad. pressure noise assuming 500W circulating power and (iii) a tarball of data and code used to generate these plots.

We took a full span measurement (to make sure there aren't any funky high-freq features) and a measurement from DC-800 Hz (where we are looking for excess noise). The DC level of light on the photodiode was 2.76V (measured using o'scope)

I'll add this to the noise budget later. But the measured RIN seems consistent with a 2013 measurement at 100Hz (though the 2013 measurement is using DTT and so doesn't have high frequency information).

Attachment 1: IMC_RIN.pdf
IMC_RIN.pdf
Attachment 2: IMC_RadPress.pdf
IMC_RadPress.pdf
Attachment 3: MC2_radPress.tgz
  13717   Thu Mar 29 12:03:37 2018 Jon RichardsonSummaryGeneralProof-of-Concept SRC Gouy Phase Measurement

I've been developing an idea for making a direct measurement of the SRC Gouy phase at RF. It's a very different approach from what has been tried before. Prior to attempting this at the sites, I'm interested in making a proof-of-concept measurement demonstrating the technique on the 40m. The finesse of the 40m SRC will be slightly higher than at the sites due to its lower-transmission SRM. Thus if this technique does not work at the 40m, it almost certainly will not work at the sites.

The idea is, with the IFO locked in a signal-recycled Michelson configuration (PRM and both ETMs misaligned), to inject an auxiliary laser from the AS port and measure its reflection from the SRC using one of the pre-OMC pickoff RFPDs. At the sites, this auxiliary beam is provided by the newly-installed squeezer laser. Prior to injection, an AM sideband is imprinted on the auxiliary beam using an AOM and polarizer. The sinusoidal AOM drive signal is provided by a network analyzer, which sweeps in frequency across the MHz band and demodulates the PD signal in-phase to make an RF transfer function measurement. At the FSR, there will be a AM transmission resonance (reflection minimum). If HOMs are also present (created by either partially occluding or misaligning the injection beam), they too will generate transmission resonances, but at a frequency shift proportional to the Gouy phase. For the theoretical 19 deg one-way Gouy phase at the sites, this mode spacing is approximately 300 kHz. If the transmission resonances of two or more modes can be simultaneously measured, their frequency separation will provide a direct measurement of the SRC Gouy phase.

The above figure illustrates this measurement configuration. An attached PDF gives more detail and the expected response based on Finesse modeling of this IFO configuration.

Attachment 1: src_gouy_phase_v3.pdf
src_gouy_phase_v3.pdf src_gouy_phase_v3.pdf src_gouy_phase_v3.pdf src_gouy_phase_v3.pdf
  13825   Tue May 8 10:24:10 2018 KiraSummaryPEMplan for this week

Here are a few things I will be working on:

  • Design PCB boards for the heater circuit and temperature sensor circuits [by wednesday]
  • Order the front panel I've designed for the seismometer block [today]
  • [next week?] install the new Acromag when it comes
  13832   Fri May 11 11:47:33 2018 johannesSummaryPEMAcromag issues

The replacement Acromag we scooped from the West Bridge E-Shop does actually seem to work, although we thought it was broken - at first it was just outputting zeros, but after I did the calibration procedure, applying +10 V and -10 V, respectively, it was reporting voltage correctly, over the full range. I don't know why the factory settings would be messed up, but it had been out of the box before. I did this only with channel 7, so you need to calibrate channels 0-6 and confirm that they indeed also work properly.

  13844   Tue May 15 15:13:23 2018 KiraSummaryPEMAcromag issues

I tried calibrating the other channels today, but they still fluctuate. Sometimes they do stabilize at +/- 10V, but then suddenly drop to 5 or 6 V before climbing back up to 10. Turning the legacy off made it go only up to 6.67V. This happens for all the channels, even after doing a factory reset and recalibrating. Not sure what's happening here.

  13865   Fri May 18 18:14:18 2018 Udit KhandelwalSummaryGeneralSummary 05/18/2018

Tip-Tilt Suspension Design:

Designed a new ECD plate and changed dimensions of the side arms after discussing with Koji. After getting feedback on the changes, I will finish the assembly and send it to him to get approved for manufacturing.

 

  13884   Wed May 23 19:24:37 2018 Udit KhandelwalSummaryGeneralSummary 05/23/2018

Tip-Tilt Redesign Project with Koji:

Did further itirations to the ECD backplate. Going to determine minimum thickness between magnet hole and plus sign for eddy current damping.

Chamber optical table layouts

Finished the positioning of optics and instruments in SolidWorks for the Vertex chambers. The reference for positioning is "40m_upgrade_layout_Dec2012.dwg", and solidworks files I created are in the main 40m CAD folder.

  13898   Wed May 30 16:12:30 2018 Jonathan HanksSummaryCDSLooking at c1oaf issues

When c1oaf starts up there are 446 gain channels that should be set to 0.0 but which end up at 1.0.  An example channel is C1:OAF-ADAPT_CARM_ADPT_ACC1_GAIN.  The safe.snap file states that it should be set to 0.  After model start up it is at 1.0.

We ran some tests, including modifying the safe.snap to make sure it was reading the snap file we were expecting.  For this I set the setpoint to 0.5.  After restart of the model we saw that the setpoint went to 0.5 but the epics value remained at 1.0.  I then set the snap file back to its original setting.  I ran the epics sequencer by hand in a gdb session and verified that the sequencer was setting the field to 0.  I also built a custom sequencer that would catch writes by the sdf system to the channel.  I only saw one write, the initial write that pushed a 0.  I have reverted my changes to the sequencer.

The gain channel can be caput to the correct value and it is not pushed back to 1.0.  So there does not appear to be a process actively pushing the value to 1.0.  On Rolfs sugestion we ran the sequencer w/o the kernel object loaded, and saw the same behavior.

This will take some thought.

  13979   Mon Jun 18 11:12:23 2018 KiraSummaryPEMfinishing up work at the lab

Since I am finishing my job at the lab, I have stored all my electronics in a box (attachment 1) and placed it under the table in the control room where some other electronics are stored. The box contains the heater circuit box, two temperature sensor boards, one temperature sensor, a short power cable and +/- 15V supply cables. In the lab I left the wires for the current setup and tied them down to the wall so that they aren't in the way (attachment 2). I left the can as is and the other temperature sensor is still attached to the inside of the can. I have labeled the wires going from the sensor as 'in' and 'out'. I've also left the wires for the heater there as well (attachment 3). I turned off the PID control and deactivated the tmux session on megatron.

Thanks to Rana and the LIGO team for giving me the opportunity to work at the 40m on this project with the seismometer.

Attachment 1: IMG_20180618_101640.jpg
IMG_20180618_101640.jpg
Attachment 2: IMG_20180618_093920.jpg
IMG_20180618_093920.jpg
Attachment 3: IMG_20180618_093932.jpg
IMG_20180618_093932.jpg
  13996   Thu Jun 21 14:23:22 2018 Udit KhandelwalSummaryGeneralA summary of the Tip-TIlt Mirror Holder design changes

Here’s a quick summary of the Tip-Tilt Design updates (all files are in the dropbox in [TipTiltSus>TT_New]) that I have been working on with Koji and Steve's help.

1. Plate on top to hold mirror in place:

The plate is 0.5 mm thick. I did a rough FEA with 10 N force on the point of pressure on it, and it bent easily.

2. Weighted screw rod at the bottom for tilting the mirror-holder:

I did a very simplified free body analysis to calculate the required length of the rod to achieve a +/- 15 mRad tilt, and got around 1.5 inches.

3. Set-screws on both side of wire clamp to adjust its horizontal position:

  • Front view (showing set screws on either side of the clamp to push it into the desired position, and the clamp in the middle with screws on top and bottom to fix its position):

  • Exploded view showing protrusion in clamp that sits in the mirror holder inset:

 

  • Exploded view showing inset in the mirror holder to slide protrusion in:

 

 

Comments:

1. Used the same screw size in most places to reduce complexity.

2. The mirror holder I have worked on is a little different from the actual piece I have on my table. Which one do you prefer (Koji)?

  13997   Thu Jun 21 14:57:59 2018 KojiSummaryGeneralA summary of the Tip-TIlt Mirror Holder design changes

> 2. Weighted screw rod at the bottom for tilting the mirror-holder:

Too long. The design of the holder should be check with the entire assembly.
We should be able to make it compact if we heavier weights.
How are these weights fixed on the shaft?
Also can we have options for smaller weights for the case we don't need such a range?
Note the mass of the weights.

> 3. Set-screws on both side of wire clamp to adjust its horizontal position:

How much is the range of the clamp motion limited by the slot for the side screws and the slot for the protrusion? Are they matched?
Can you show us the design of the slot made on the mirror holder?

>>

Where is the center of mass (CoM) for the entire mirror holder assy and how much is the height gap between the CoM and the wire release points. Can you do this with 3/8" and 1/2" fused silica mirrors?

  14014   Mon Jun 25 19:14:02 2018 UditSummaryGeneralRe: A summary of the Tip-TIlt Mirror Holder design changes

2. Weighted screw rod at the bottom for tilting the mirror-holder:

The screw length selected here (2") is not interfering with any part of the assembly.

The 'weights' I have here are just thumb nuts from Mcmaster, so their weight is fixed (1.65g each, btw).

Problem I'd like to solve: Find an assortment of weighted, symmetric nuts with caps on one end to fix position on shaft. 

3. Set-screws on both side of wire clamp to adjust its horizontal position:

Thanks for pointing out the mismatch in travel distance of protrusion and clamp screws. To match them, the clamp screw slot now sticks out of the profile (by 1.5mm). The range of the clamp motion is +/- 3 mm.

Also, here's a screenshot of the slot in the mirror holder:

--

- Excluding the weighted screw rod assembly, the height gap between assembly COM and wire release point is 3.1 mm.

Quote:

> 2. Weighted screw rod at the bottom for tilting the mirror-holder:

Too long. The design of the holder should be check with the entire assembly.
We should be able to make it compact if we heavier weights.
How are these weights fixed on the shaft?
Also can we have options for smaller weights for the case we don't need such a range?
Note the mass of the weights.

> 3. Set-screws on both side of wire clamp to adjust its horizontal position:

How much is the range of the clamp motion limited by the slot for the side screws and the slot for the protrusion? Are they matched?
Can you show us the design of the slot made on the mirror holder?

>>

Where is the center of mass (CoM) for the entire mirror holder assy and how much is the height gap between the CoM and the wire release points. Can you do this with 3/8" and 1/2" fused silica mirrors?

 

  14015   Mon Jun 25 21:14:08 2018 KojiSummaryGeneralRe: A summary of the Tip-TIlt Mirror Holder design changes

3.
- Do we need this much of extended range of the clamp location? How much range will we need if we use either 3/8 or 1/4 inch mirrors?
- This slot on the mirror holder ring is not machinable.

About the CoM height
- Include the angle adjustment screw and adjust the wire releasing point to have comparable pitch resonant freq to the SOS suspension.

 

  14042   Fri Jul 6 19:39:37 2018 Udit KhandelwalSummaryGeneralCAD drawings of cantilever suspension required

Request to Koji to acquire the drawings or 3D CAD of the cantilever suspensions of the Tip-Tilt Assembly!

  14044   Sun Jul 8 12:20:12 2018 JonSummaryAUXGouy Phase Measurements from AUX-Laser Scans

This note reports analysis of cavity scans made by directly sweeping the AUX laser carrier frequency (no sidebands). The measurement is made by sweeping the RF offset of the AUX-PSL phase-locked loop and demodulating the cavity reflection/transmission signal at the offset frequency.

Y-Arm Scan

Due to the simplicity of its expected response, the Y-arm cavity was scanned first as a test of the AUX hardware and the sensitivity of the technique. Attachment 1 shows the measured cavity transmission with respect to RF drive signal.

The AUX laser launch setup is capable of injecting up to 9.3 mW into the AS port. This high-power measurement is shown by the black trace. The same measurement is repeated for a realistic SQZ injection power, 70 uW, indicated by the red curve. At low power, the technique still clearly resolves the FSR and six HOM resonances. From the identified mode resonance frequencies the following cavity parameters are directly extracted.

YARM Gautam's Finesse Model Actual
FSR 3.966 MHz 3.967 MHz
Gouy phase 54.2 deg 52.0 deg

PRC Scan

An analogous scan was performed for the PRC, with the IFO locked on PSL carrier in PRMI. Attachment 2 shows the measurement of PRC transmission with respect to drive signal.

The scan resolves HOM resonances to at least ~13th order, whose frequencies yield the following cavity parameters.

PRC Gautam's Finesse Model Actual
FSR 22.30 MHz 22.20 MHz
Gouy phase 13.4 deg 15.4 deg

SRC Scan

Ideally (and at the sites) the SRC mode resonances will be measured in SRMI configuration. Because every other cavity is misaligned, this configuration provides an easily-interpretable spectrum whose resonances can all be attributed to the SRC.

Due to time constraints at the 40m, the IFO could not be restored to lockability in SRMI. It has been more than two years since this configuration was last run. For this reason the scan was made instead with the IFO locked in DRMI, as shown in Attachment 3. The quantity measured is the AUX reflection with respect to drive signal.

This result requires far more interpretation because resonances of both the SRC and PRC are superposed. However, the resonances of the PRC are known a priori from the independent PRMI scan. The SRC mode resonances identified below do not conincide with any of the first five PRC mode resonances.

Based on the identified mode resonance frequencies, the SRC parameters are measured as follows.

SRC Gautam's Finesse Model Actual
FSR 27.65 MHz 27.97 MHz
Gouy phase 10.9 deg 8.8 deg

Lessons Learned

From experience with the 40m, the main challenges to repeating this measurement at the sites will be the following.

  • Pointing jitter of the input AUX beam. This causes the PSL-AUX beam overlap to vary at transmission (or reflection), causing variation in the amplitude of the AUX-PSL beat note. As far as we can tell, the frequency of the resonances (the only object of this measurement) is not changing in time, only the relative amplitudes of the diferent mode peaks. I believe the SQZ alignment loops will mitigate this problem at the sites.
  • Stabilization of the network analyzer time base. We found the intrinsic frequency stability of the network analyzer (Agilent 4395A) to be unacceptably large. We solved this problem by phase-locking the Agilent to an external reference, a 10-MHz signal provided by an atomic clock.
Attachment 1: yarm_aux_carrier_trans.pdf
yarm_aux_carrier_trans.pdf
Attachment 2: prmi_aux_carrier_trans.pdf
prmi_aux_carrier_trans.pdf
Attachment 3: drmi_aux_carrier_trans.pdf
drmi_aux_carrier_trans.pdf
  14047   Mon Jul 9 17:29:28 2018 Udit KhandelwalSummaryTip-TIltTipTilt mirror holder final changes

Final Summary of changes to mirror holder in Tip-Tilt holder.

Determining minimum range for Side Clamp:

1. The initial distance b/w wire-release point and mirror assembly COM = 0.265 mm


2. But this distance is assuming that wire-release point is at mid-point of clamp. So I'm settling on a range of +/- 1mm. The screenshots below confirm range of ~1mm between (1) side screw & protrusion and (2) clamp screw and clamp.

Determining length of tilt-weight assembly rod at the bottom to get \pm 20mRad range

The tilt-weight assembly is made from following Mcmaster parts:
Rod   - 95412A864 18-8 SS  #2-56 Threaded Rod
Nuts  - 91855A103 18-8 SS #2-56 Acorn Cap Nut

Since the weights are fixed, only rod length can be changed to get the angle range.

tan \theta =\frac{d}{h}

d= h \times tan\theta = 34.25\text{mm} \times tan(20 \text{mRad}) = 0.69 \text{mm}
So a range of 1 mm between nut's inner face and mirror-holder face should be enough. Since holder is 12 mm thick, rod length = 12mm + 2 x 1mm + 2 x (nut length) = 12 + 2 + 9.6 = 23.6 mm = 0.93 inch. So a 1" rod from Mcmaster will be fine.

Attachment 4: 2-1.png
2-1.png
  Draft   Wed Jul 11 18:13:19 2018 keerthanaSummaryAUXGouy Phase Measurements from AUX-Laser Scans

From the Measurement Jon made, FSR is 3.967 MHz and the Gouy phase is 52 degrees. From this, the length of the Y-arm cavity seems to be 37.78 m and the radius of curvature of the mirror seems to be 60.85 m.

 

Guoy Phase = \cos^{-1} \sqrt{g1.g2}

\\ g = 1- \frac{L}{R}

L = \frac {c} {2*FSR}

FSR = Free spectral Range

L = Lenth of the arm

R = Radius of curvature of the mirror (R1 =\infty  , R2= unknown)

Quote:

This note reports analysis of cavity scans made by directly sweeping the AUX laser carrier frequency (no sidebands). The measurement is made by sweeping the RF offset of the AUX-PSL phase-locked loop and demodulating the cavity reflection/transmission signal at the offset frequency.

Y-Arm Scan

Due to the simplicity of its expected response, the Y-arm cavity was scanned first as a test of the AUX hardware and the sensitivity of the technique. Attachment 1 shows the measured cavity transmission with respect to RF drive signal.

The AUX laser launch setup is capable of injecting up to 9.3 mW into the AS port. This high-power measurement is shown by the black trace. The same measurement is repeated for a realistic SQZ injection power, 70 uW, indicated by the red curve. At low power, the technique still clearly resolves the FSR and six HOM resonances. From the identified mode resonance frequencies the following cavity parameters are directly extracted.

YARM Gautam V. Finesse Model Actual
FSR 3.966 MHz 3.967 MHz
Gouy phase 54.2 deg 52.0 deg

 

 

  14069   Fri Jul 13 20:36:33 2018 KojiSummaryGeneralIn vac/In air heater wiring

I went to the Y-end and took more photos of the cable stand. These revealed that in-vac pin #13 is connected to the shield of the cable (P.2). This in-vac pin #13 corresponds to  in-air pin #1. So in the end, we bunch the pins in the following order.

In Air In Vac
Pin #2-7 Pin #12-7
Pin #8-13 Pin #6-1
Pin #14-19 Pin #25-20
Pin #20-25 Pin #19-14

 

Attachment 1: heater_wiring.pdf
heater_wiring.pdf heater_wiring.pdf heater_wiring.pdf
  14073   Mon Jul 16 15:07:19 2018 KojiSummaryVACOven C vent

[Steve Koji]

- Attachment1: Removed the thermal cap. Checked the temperature of the oven. It was totally cold.

- Attachment2: Confirmed the RGA section was isolated. The pumps for the RGA was left running.

- Attachment3: Closed the main valve. The pumps for the main volume was left running.

- Attachment4: Started removing the rid. This did not change the gause readings as they were isolated from the venting main volume.

- Attachment5: Opened the rid. Took the components out on a UHV foil bag. The rid was replaced but loosely held by a few screws with the old gasket, just to protect the frange and the volume from rough dusts.

Attachment 1: P_20180716_141512.jpg
P_20180716_141512.jpg
Attachment 2: P_20180716_141601.jpg
P_20180716_141601.jpg
Attachment 3: P_20180716_141610.jpg
P_20180716_141610.jpg
Attachment 4: P_20180716_141827.jpg
P_20180716_141827.jpg
Attachment 5: P_20180716_143901.jpg
P_20180716_143901.jpg
  14077   Tue Jul 17 12:55:45 2018 KojiSummaryGeneralStarted pumping

[Steve, Koji, Gautam]

We started pumping down at ~12:15PM.

Vent finalization ~ YEND

  • The table leveling was way off. This was adjusted by the balancing weight. (Attachment 1~3)
  • The alignment of ETMY was not too much off. Just aligned it with the oplev spot on MEDM and this already made the green flashing.
  • The Green TEM00 was maximized with ITMY and ETMY. This made the PSL IR flashing.
  • The heater wires were checked. I found that one of the heater wires was touching the optical table via the cable shield. This is because the upper pins were shifted to the left side (Attachment 4&5). The pins were shifted and now all 4 cables are isolated form the table. I also checked the mutual resistance between the 4 terminals. They were measured to be isolated except two pairs that showed 4.4 Ohms and 4.0 Ohms (Attachment 6)
  • The tools were removed from the chamber. The Y arm was still flashing.
  • We closed the ETMY door.

Vent finalization ~ Vertex

  • Found the ITMX stuck. Gautam came in and showed us his black magic to release the optic...
  • This allowed us to align X arm. The green flash was found and the TEM00 flash was seen. This allowed us to see the PSL IR flash at the X end.
  • PRM Refl was aligned. SRM was aligned with the oplev.
  • The beam on the AS port was checked. The AS beam came out from the window.
  • Closed the OMC chamber.

Pumping

  • Started pumping with RP1 and RP3. (~12:15PM)

Attachment 1: IMG_5408.JPG
IMG_5408.JPG
Attachment 2: IMG_5400.JPG
IMG_5400.JPG
Attachment 3: IMG_5401.JPG
IMG_5401.JPG
Attachment 4: IMG_5402.JPG
IMG_5402.JPG
Attachment 5: IMG_5403.JPG
IMG_5403.JPG
Attachment 6: IMG_5404.JPG
IMG_5404.JPG
  14079   Tue Jul 17 18:16:38 2018 SteveSummaryVACpumpdown 81 at 6 hrs

Precondition:  4 days at atm.   Atm5

HEPA tent used during the vent at ETMY  It reduced partical count 10 fold of 0.5 and 0.3 micron particals. Atm6

New items in vacuum:  Clean manual gate valve [Cetec made] from John Worden with 6" id....as it came from Hanford... [ Throttle able gate valve- TGV ] Atm3

                                 ( note: we have 3 more identical in the lab. The original intention was to use them for purging gates )

                                  Optiform Au plated reflector , Induceramics heating elements, similar as existing Cooner cables and related lenses, hardwear. see 14078

                                  OMC related item : none......... 14,110

 

The pumpdown is at 510 mTorr with RP1 & RP3 still pumping. Koji will shut it down the roughing later tonight. Tomorrow morning I will start the pumping by switching over to TP1 maglev.

Thanks for Koji and Gautam'  help of the installation of the manual gate valve. Atm4  This will allow us to control the load on our Varian foreline D70 turbo TP3

 

Attachment 1: pd81@6hrs.png
pd81@6hrs.png
Attachment 2: before_c.jpg
before_c.jpg
Attachment 3: tgv_c.jpg
tgv_c.jpg
Attachment 4: TGVinstalled.jpg
TGVinstalled.jpg
Attachment 5: 4_days_vent.png
4_days_vent.png
Attachment 6: tentHEPA.jpg
tentHEPA.jpg
  14080   Tue Jul 17 22:25:41 2018 KojiSummaryVACpumpdown 81 at 6 hrs

10:20PM

  • Opened VM2 to pump down the RGA section with TP1
  • Stopped rotary roughing pumps
    • Manually closed RV1
    • Closed V3
    • Stopped RP1 and RP3
    • Vented the RP hose

The P1 pressure is 380mTorr. I allowed Gautam to use the full PSL power (~1W).

  14082   Wed Jul 18 12:49:08 2018 SteveSummaryVACpumpdown 81 at 6 +4.5hrs

The manual gate valve scan was clean. Atm1     TP1 was pumping on it overnight.

                                                Pumpdown continued to hand over the pumping to TP1 maglev turbo

V1 was opened at P1 400 mTorr  with manual gate at 3/4 turn open position as Magev at 560 Hz rotation.

Two aux fans on to hold tubo temps TP1 & TP3 . Atm3

This is the first time we pumping down from atm with ONE small "beer can" turbo  and throttled gate valve to control load on small turbo forepump

The 70 l/s turbo is operating at 50k RPM, 0.7 A and 31 C,  pumping speed  ~ 44 mTorr/h at 200-400 mTorr range with aux drypump in the foreline of TP3

Watching foreline pressures and current one can keep opening gate valve little by little the so the load is optimized. It is working but not fast.

Let's keep small turbo at 0.8 Amp and 32 C max at this pumpdown. 

Quote:

10:20PM

  • Opened VM2 to pump down the RGA section with TP1
  • Stopped rotary roughing pumps
    • Manually closed RV1
    • Closed V3
    • Stopped RP1 and RP3
    • Vented the RP hose

The P1 pressure is 380mTorr. I allowed Gautam to use the full PSL power (~1W).

Attachment 1: manlGateScan.png
manlGateScan.png
Attachment 2: handing_over_Mag.png
handing_over_Mag.png
Attachment 3: TGVw2auxfans_.jpg
TGVw2auxfans_.jpg
  14083   Wed Jul 18 17:36:50 2018 SteveSummaryVACpumpdown 81 at 6 +9 hrs completed

IFO P1 6e-4 Torr,  manual gate valve is fully open

The annuloses will be pumped down tomorrow.

Valve configuration: vacuum normal, RGA and annuloses are not pumped

Quote:

The manual gate valve scan was clean. Atm1     TP1 was pumping on it overnight.

                                                Pumpdown continued to hand over the pumping to TP1 maglev turbo

V1 was opened at P1 400 mTorr  with manual gate at 3/4 turn open position as Magev at 560 Hz rotation.

This is the first time we pumping down from atm with one small "beer can" turbo  and throttled gate to control load on small turbo forepump

The 70 l/s turbo is operating at 50k RPM, 0.7 A and 31 C,  pumping speed  ~ 44 mTorr/h at 200-400 mTorr range.

Watching foreline pressures and current one can keep opening gate valve little by little the so the load is optimized. It is working but not fast.

Let's keep small turbo at 0.8 Amp and 32 C max at this pumpdown. 

Quote:

10:20PM

  • Opened VM2 to pump down the RGA section with TP1
  • Stopped rotary roughing pumps
    • Manually closed RV1
    • Closed V3
    • Stopped RP1 and RP3
    • Vented the RP hose

The P1 pressure is 380mTorr. I allowed Gautam to use the full PSL power (~1W).

Attachment 1: pd81completed.png
pd81completed.png
Attachment 2: pd81@30hrs.png
pd81@30hrs.png
  14085   Thu Jul 19 01:56:25 2018 gautamSummaryVACAUX pump shutdown

[koji, gautam]

Per Steve's instructions, we did the following:

  • TP3fl pressure reading was 65 torr.
  • TP3 controller reported pumping current of ~0.18A, temperature of 24C.
  • We throttled the manual valve which was connecting the "AUX" pump to the TP3fl.
  • The TP3fl pressure went up to 330 torr.
  • TP3fl controller reported current of 0.22A, temperature of 24C.
  • After ~5mins, we shut the AUX pump off.
  • We have monitored it over the last 1hour, no red flags.
    • (Before stopping AUX RP)
      0:56AM TP3 I=0.18A, P=6W, 23degC, TP3FL: 66
    • 0:59AM TP3 I=0.22A, P=7W, 23degC, TP3FL: 336
    • 1:15AM TP3 I=0.21A, P=7W, 23degC, TP3FL: 320
    • 1:31AM TP3 I=0.21A, P=7W, 23degC, TP3FL: 310
    • 2:06AM TP3 I=0.21A, P=7W, 23degC, TP3FL: 301
    • 5:06AM TP3 I=0.21A, P=7W, 23degC, TP3FL: 275
  14086   Thu Jul 19 04:44:09 2018 Annalisa, TerraSummaryThermal Compensationfrequency shift observed with heating!

Annalisa, Gautum, Koji, Terra

Summary: with the reflector setup, we measured a frequency shift of the first and second order modes! First looks of shifts show 1st HOM shift ~-10 kHz, 2nd HOM shift ~-18 kHz (carrier ~4 kHz). We saw no shift with the cylinder/lenses set up.

- - - - -

Tonight we modified the cavity scan setup: the LO is provided by the Marconi which, at the same time, is also used to scan the AUX laser frequency instead of the Agilent. In order to get rid of the free running noise between Marconi and Agilent, the Marconi frequency was scanned and, point by point, the Agilent center frequency was changed accordingly. In order to speed up the process, the whole procedure was automated. The script is called AGfast.py and can be found in /users/annalisa/postVent.

One thing that helped in improving the data quality of the phase information was to set the Agilent IF bandwidth @1kHz. Not yet clear why, but it was better than having a lower bandwidth. To be further investigated.

With this setup, we made some coarse scan of the full FSR and then we "zoomed" around the main peaks in order to increase the resolution and get a more precise information about the peak frequency.

Here are the frequency ranges that we scanned:

  • carrier - central frequency: 31.73MHz; range: [31.68MHz - 31.78MHz]
  • HOM1 - central frequency: 32.88MHz; range: [32.84MHz - 32.93MHz]
  • HOM2 - central frequency: 34.03MHz; range: [33.95MHz - 34.06MHz]
  • HOM3 - central frequency: 35.18MHz; range: [35.09MHz - 35.25MHz]

We powered the heater of the lenses setup @4:55 am at 14.4V and 0.9A. Then we slightly increased the power @5:05am and the final "hot state" configuration is with heater powered at 16V and 0.9A.

With this setup we couldn't see any frequency shift

Then, at around 6:30 am we turned on the reflector setup and we measured a frequency shift of the first and second order modes. First scans show 1st HOM shift ~10 kHz, 2nd HOM shift ~18 kHz. First attachment shows carrier hot/cold, second attachment shows HOM2 hot/cold. We started to get plauged by high seismic noise. Heaters turned off at 7:45 am. Lots of scans and actual analysis to go.


gautam: about the questionable plotting -

  • 10 faint (alpha~0.3) lines are individual measurements with the reflector doing its heating. (AG4395A, 0 span, single frequency measurements plotted together).
  • charcoal line, labelled mean, is the mean of the 10 above lines.
  • bright green ("Reference") is the mean of a coarse scan (cold ETM) overlaid for comparison. 
  • "cold" - self explanatory.

My personal favourite plot is Attachment #3, which is a 5 MHz scan (cold) to identify positions of the various peaks. The power of including phase information in the analysis is clear. The second FSR on the right edge of the plot is not as prominent as the first is because the arm transmission was degrading throughout the measurement. For future measurements, we should consider locking the IMC length to the arm cavity - this would eliminate such alignment drifts, and maybe also make the PLL control signal RMS smaller. 

Attachment 1: scanning_fine_2018-07-19-07-32-08_parsed.pdf
scanning_fine_2018-07-19-07-32-08_parsed.pdf
Attachment 2: scanning_fine_2018-07-19-06-57-47_parsed.pdf
scanning_fine_2018-07-19-06-57-47_parsed.pdf
Attachment 3: Yscan_scanning_parsed_2am.txt.pdf
Yscan_scanning_parsed_2am.txt.pdf
  14087   Thu Jul 19 11:01:03 2018 SteveSummaryVACpd81 @ 2e-5 Torr

Cold cathode gauge just turned on.

Attachment 1: pd81@2days.png
pd81@2days.png
  14088   Thu Jul 19 13:35:30 2018 SteveSummaryVACannuloses pumped

Roughing down the annuloses required closing V1 for 13 minutes

IFO is 2.2e-5 Torr

Attachment 1: AnsPumped.png
AnsPumped.png
  14090   Fri Jul 20 07:43:54 2018 SteveSummarySUSETMY

 

 

Attachment 1: ETMY_leveling.png
ETMY_leveling.png
Attachment 2: ETMY.png
ETMY.png
  14094   Sat Jul 21 01:06:49 2018 gautamSummaryThermal CompensationY arm locking

I implemented this today. For now, the LSC output matrix is set to actuate on MC2 for Y arm locking. As expected, the transmission was much more stable, and the PLL control signal RMS was also reduced by factor of ~3. MC2 control signal does pick up a large (~2000 cts) DC component over a few hours, so we need to relieve this periodically.

Now that we have a workable ASS for the Y arm as well, we should be able to have more confidence in returning to the same beam spot position on the ETM and staying there during a scan using this technique.

The main improvement to be trialled next in the scanning is to improve the speed of scanning. As things stand, my script takes ~2.5 seconds per datapoint. If we can cut this in half, that'd be huge. On Wednesday night, we were extraordinarily lucky to avoid MC3 glitching, EPICS/slow machine failures, and GPIB freezes. Today, the latter reared its head. Fortunately, since I'm dumping data to file for each datapoint, this means we at least have data till the GPIB freeze.

Quote:

For future measurements, we should consider locking the IMC length to the arm cavity - this would eliminate such alignment drifts, and maybe also make the PLL control signal RMS smaller. 


Not related to this work: Terra, Sandrine, Keerthana and I cleaned up the lab a bit today, and made better cable labels. Aaron and I have to clean up the OMC area a bit. Huge thanks to Steve for taking care of our mess elsewhere in the lab!

  14096   Sat Jul 21 14:03:19 2018 KojiSummaryThermal CompensationY arm locking

Ah. With MC2 feedback, we have about 3 times smaller "optical gain" for the ASS A2L. We have same dither, same actuator, but we need only 1/3 actuation of the MC2 compared to the ETMY case.
We had to reduce the ASS spot servo from 1 to 0.3 to make is stable, so this means that the ASS is really merginally stable.

  14098   Mon Jul 23 09:58:52 2018 SteveSummaryVACRGA scan at day 6

 

 

Attachment 1: pd81-560Hz-d6.png
pd81-560Hz-d6.png
  14103   Wed Jul 25 14:45:59 2018 SandrineSummaryThermal CompensationETM Y Table AUX read out

Attached is a photo of the set up of the ETM Y table showing the AUX read out set up. 

Currently, the flip mount sends the AUX to the PDA255. Terra inserted a razor blade so the PDA255 will witness more HOMs. The laser is also sent to the regular PD and the CCD.

Attachment 1: EY_table_.JPG
EY_table_.JPG
ELOG V3.1.3-